1. Field of the Invention
The present invention relates to liquid crystal display devices, and more particularly, to a display device having a through hole in the screen, in which another display can be provided or an object can be inserted.
2. Description of the Related Art
It is widely practiced in slot-machine-type game machines or the like that liquid crystal display devices have a fixed area of transparent portion at part of the screen, at which another display is provided. Slot-machine-type game machines have three rotating drums in the center of the surface facing the player, the rotation axes being in agreement with one another in the horizontal direction. The rotating drums are rotated by pressing a start button, and then stopped in sequence by pressing stop buttons corresponding to the rotating drums.
Mainstream liquid crystal display devices for use in display devices have a structure in which part of the color filter of the liquid crystal panel is removed, the polarizer and the optical sheet of the back light are bored, and the light guide of the backlight and part of the optical sheet are partially made transparent so that the back of the liquid crystal display device can be seen through. An example of this technique is disclosed in JP-A-2004-329687 (Patent Document 1).
Another technique of forming holes in liquid crystal display devices used in pachinko machines, through which pachinko balls are passed, is disclose, for example, in JP-A-11-89995 (Patent Document 2). Another technique of forming a hole in the center of liquid crystal display panels for use in watches, in which the shafts of hands in watches are passed, is disclosed in JP-A-11-305246 (Patent Document 3).
With the structure of the present display devices, the portion to be transparent for another display has layers of glass or sheet. This structure leads to a decrease in transparency of the portion to be transparent or reflection or leakage of light from the backlight, affecting the visibility of the back. Although Patent Document 1 describes a display device having holes in the liquid crystal display panel and the backlight, a concrete practical structure is not disclosed and is not in practical use in the present.
Patent Document 2 discloses a technique of forming simple holes in a liquid crystal display panel. However, Patent Document 2 provides no disclosure and suggestion on the problem of mechanical breakage around the hole of the liquid crystal display panel. It also provides no suggestion on application to a complicated structure in which a liquid crystal display panel having a backlight and capable of various image displays can provide another display.
The technique described in Patent Document 3 is for special use such as watches. It provides no suggestion on application to large liquid crystal display devices having a backlight and capable of another display on the display screen.